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D. Belt Tensions and Adjustments
Belt tension is adjusted during the initial run-in and test
periods at the factory. However, the belts are run as
slack as possible to prevent excessive damage to the
bearings, yet tight enough to prevent slippage.
It is necessary, therefore, to tighten all belts during the
first few months of operation, and to check for proper
tension weekly during the first 60 days, after which
30-day check intervals are sufficient.
NOTE: Turn off all power to the equipment before
checking belt tensions.
CAUTION: Do not attempt to tighten any belt or
belts by changing the pitch of an adjustable pulley,
as this will change the speed of a driven pulley,
causing the unit to be rendered OUT OF AIR
BALANCE. Do not overtighten belts.
Suggested Belt Tension Method
1. Check tension frequently during the first 24-48
hours of run-in operation. Ideal tension is the
lowest tension at which the belt will not slip under
peak load conditions. Over tensioning shortens belt
and bearing life.
2. To properly tension a conventional V-belt drive use
the following procedure:
a. Measure the span length.
b. At the center of the span, apply a force perpen-
dicular to the span to deflect the belt 1/64 inch
for every inch of span length. For example, for a
40 inch span, apply a force that will deflect the
belt 40/64 or 5/8 of an inch.
c. Compare the force you have applied with the
values given in the table below. If the force is
between the values for normal tension and 1-1/2
times normal tension, the belt tension should be
satisfactory. If the belt tension is not within this
range, it can be adjusted by loosening the motor
mounting bolts, and adjusting the position of the
motor along its base.
NOTE: A new drive can be tightened to two times
the minimum value shown to allow for normal drop
in tension during the run-in period.
B Section
small
Pounds
pulley
Pounds
Force for
diameter
Belt
Force for
1
1
/
2
times
range in
Manufacturer
Normal
Normal
Inches
& Type Belt
Tension
Tension
3.4-4.2
Gates Hi-Power
4.4
6.6
4.4-4.6
Gates Hi-Power
4.9
7.4
5.8-8.6
Gates Hi-Power
5.8
8.7
Note: For recommendation of other types of belts,
consult respective manufacturers.
E. Optional Coils And Related Items
1. Coils – Coil surfaces must be kept clean of dirt and
lint in order to operate at rated efficiency. Coils
should be inspected on a regular basis and
cleaned as required.
CAUTION: Solutions used to clean coils must not
be corrosive to metals or materials used in the
manufacturer of this equipment. If cleaning
solutions are applied through means of high
pressure spray, care must be taken to avoid
damaging the coil fins.
2. Condensate Drain Pan – Periodically flush the
condensate pan and drain system with a water
hose.
F. Gaskets
Gaskets are used on doors, inspection covers, some
filter racks, and some outdoor air dampers. Inspect
gaskets periodically and repair or replace as required.
